<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>Seek to a position</title>
<link media="all" rel="stylesheet" type="text/css" href="styles/03e73060321a0a848018724a6c83de7f-theme-base.css" />
<link media="all" rel="stylesheet" type="text/css" href="styles/03e73060321a0a848018724a6c83de7f-theme-medium.css" />

 </head>
 <body class="docs"><div class="navbar navbar-fixed-top">
  <div class="navbar-inner clearfix">
    <ul class="nav" style="width: 100%">
      <li style="float: left;"><a href="splfileobject.fscanf.html">« SplFileObject::fscanf</a></li>
      <li style="float: right;"><a href="splfileobject.fstat.html">SplFileObject::fstat »</a></li>
    </ul>
  </div>
</div>
<div id="breadcrumbs" class="clearfix">
  <ul class="breadcrumbs-container">
    <li><a href="index.html">PHP Manual</a></li>
    <li><a href="class.splfileobject.html">SplFileObject</a></li>
    <li>Seek to a position</li>
  </ul>
</div>
<div id="layout">
  <div id="layout-content"><div id="splfileobject.fseek" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">SplFileObject::fseek</h1>
  <p class="verinfo">(PHP 5 &gt;= 5.1.0, PHP 7, PHP 8)</p><p class="refpurpose"><span class="refname">SplFileObject::fseek</span> &mdash; <span class="dc-title">Seek to a position</span></p>

 </div>

 <div class="refsect1 description" id="refsect1-splfileobject.fseek-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="modifier">public</span> <span class="methodname"><strong>SplFileObject::fseek</strong></span>(<span class="methodparam"><span class="type">int</span> <code class="parameter">$offset</code></span>, <span class="methodparam"><span class="type">int</span> <code class="parameter">$whence</code><span class="initializer"> = <strong><code>SEEK_SET</code></strong></span></span>): <span class="type">int</span></div>

  <p class="para rdfs-comment">
   Seek to a position in the file measured in bytes
   from the beginning of the file, obtained by adding
   <code class="parameter">offset</code> to the position specified by
   <code class="parameter">whence</code>.
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-splfileobject.fseek-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>
    
     <dt>
<code class="parameter">offset</code></dt>

     <dd>

      <p class="para">
       The offset. A negative value can be used to move backwards through the file which
       is useful when SEEK_END is used as the <code class="parameter">whence</code> value.
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">whence</code></dt>

     <dd>

      <p class="para">
       <code class="parameter">whence</code> values are:
       <ul class="simplelist">
        <li class="member"><strong><code>SEEK_SET</code></strong> - Set position equal to <code class="parameter">offset</code> bytes.</li>
        <li class="member"><strong><code>SEEK_CUR</code></strong> - Set position to current location plus <code class="parameter">offset</code>.</li>
        <li class="member"><strong><code>SEEK_END</code></strong> - Set position to end-of-file plus <code class="parameter">offset</code>.</li>
       </ul>
      </p>
      <p class="para">
       If <code class="parameter">whence</code> is not specified, it is assumed to be <strong><code>SEEK_SET</code></strong>.
      </p>
     </dd>

    
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-splfileobject.fseek-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   Returns 0 if the seek was successful, -1 otherwise. Note that seeking
   past EOF is not considered an error.
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-splfileobject.fseek-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-3712">
    <p><strong>示例 #1 <span class="methodname"><strong>SplFileObject::fseek()</strong></span> example</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$file&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">SplFileObject</span><span style="color: #007700">(</span><span style="color: #DD0000">"somefile.txt"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Read&nbsp;first&nbsp;line<br /></span><span style="color: #0000BB">$data&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$file</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">fgets</span><span style="color: #007700">();<br /><br /></span><span style="color: #FF8000">//&nbsp;Move&nbsp;back&nbsp;to&nbsp;the&nbsp;beginning&nbsp;of&nbsp;the&nbsp;file<br />//&nbsp;Same&nbsp;as&nbsp;$file-&gt;rewind();<br /></span><span style="color: #0000BB">$file</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">fseek</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>
  </p>
 </div>


 <div class="refsect1 seealso" id="refsect1-splfileobject.fseek-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.fseek.html" class="function" rel="rdfs-seeAlso">fseek()</a> - 在文件指针中定位</span></li>
   </ul>
  </p>
 </div>


</div></div></div></body></html>